Muscle Contractions, Part 3: How to Use Them - Practical

by Dr. Rob Orr |   Date Released : 20 Oct 2010
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Dr. Rob Orr

About the author: Dr. Rob Orr

Dr. Rob Orr joined the Australian Army in 1989 as an infantry soldier before transferring to the Defence Force Physical Training Instructor (PTI) stream. Serving for 10 years in this stream, Rob designed, developed, instructed and audited physical training programs and physical education courses for military personnel and fellow PTIs from both Australian and foreign defence forces. Rob subsequently transferred to the physiotherapy stream where his role included the clinical rehabilitation of defense members and project management of physical conditioning optimisation reviews. Serving as the Human Performance Officer for Special Operations before joining the team at Bond University in 2012, Rob continues to serve in the Army Reserve as a Human Performance Officer and as a sessional lecturer and consultant. Rob is also the co-chair of Tactical Strength and Conditioning (TSAC) – Australia.

Rob’s fields of research include physical conditioning and injury prevention for military and protective services from the initial trainee to the elite warrior. Generally focussing on the tactical population, Rob is actively involved in research with the Australian and foreign defense forces, several police departments (both national and international), and firefighters.

The results of Rob’s work and academic research have been published in newspapers, magazines and peer-reviewed journals and led to several health and safety awards. In addition, Dr. Orr serves as the section editor for the Australian Strength and Conditioning Journal – TSAC Section and the shadow editor for the National Strength and Conditioning Association (NSCA) TSAC Technical Report. Rob is regularly invited to deliver training workshops and present at conferences both nationally and internationally.

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Comments (3)

Wahid, Nabil | 25 Oct 2010, 23:44 PM

Dear Rob,

Thanks alot for your time you spend to explain things in more details. i will read your answer more than one time, and if i have any point i am not sure about i will ask. thanks again.

Orr, Dr. Rob | 25 Oct 2010, 20:26 PM

Dear Nabil, Thanks for the question.
It seems that text information you provided is crossing absolute and relative factors (or taken from two different sections). Whereas the first sentence discusses time under tension the second discusses absolute loads (oranges and apples). If we forget the first sentence for a minute and focus from the second sentence on…The second sentence is acknowledged in this article series, being; 1. Eccentric contractions utilize less energy than concentric contractions and 2. Eccentric contractions being 20-50 % stronger than concentric contractions. So yes, ‘…if load is constant, less tension is generated during the eccentric phase...’ As for the third sentence about increasing load, this is a given for all contractions, eccentric, isometric, concentric, isoinertial/isotonic and isokinetic... increased load=increased tension (all other parameters remaining extant). The last two sentence are correct in a general sense, but what if the athlete recovering from a musculoskeletal injury participates in a high demand sport that requires these movements? Personally I would include this form of training as part of the end phase return-to-sport rehabilitation process following injury.

Now to the first sentence. As mentioned above it is not placed in perspective – apple versus orange (Unfortunately, I cannot access this text until I return to AUST in 2011 so I cannot myself place it in the full context it was presented). The statement ‘…during high-intensity resistance training is to assume that if a weight is lifted quickly (concentric contraction) and lowered slowly (eccentric contraction), the slow eccentric contraction generates greater tension…’ does not explain what the tension generated is compared to? For example are they saying that a slower eccentric contraction does not create greater tension for the same overall repetition using a faster eccentric contraction? Or are they comparing a slower eccentric contraction to a faster concentric contraction? I am presuming the later. In which case I have yet to find a study that compares MUSCLE TENSION for 3-2-1 contractions against 1-1-1 contractions (There are studies that compare 5-1 and 1-5 and similar but again these parameters are significantly different from those discussed in Part 3 and most DO NOT measure muscle tension, but force output, hormonal and metabolic differences, heart rates etc) – Does the text you mentioned reference this statement? Secondly, the text appears to assume that this is why the eccentric contractions are slowed, when in effect it is not. The intent of slowing the eccentric contraction is to increase the tension within the muscle during a ‘given’ load. So, as you are ‘stronger’ eccentrically slowing the movement down during the eccentric contraction will increase muscle tension more than a faster movement during the eccentric contraction (ie increasing time-under-tension). This has been shown in the research.

When lowering (or raising) more slowly the amount of tension developed has to increase as time-under-tension increases. Therefore, the intent is not to slow down eccentric contractions to equal the tension of the concentric contraction but to increase the tension of the eccentric contraction. So when training with a given load – as most people do (as the average person does not alter load during contractions) – to increase tension we slow down the contractions that are stronger. So in effect a 3-2-1 would have to generate more tension than a 1-1-1.

Now at last back to your specific question. Do both factors have the same influence on tension. No, I believe that each does have an impact on tension development but to dictate whether they have the same influence would be a grand assumption as there are too many other factors that will have an impact. For example, if the lifter has limited experience they may not be technically capable of lifting a heavier load with correct technique or if they have a low OBLA/Lacate tolerance they may not be able to continue to work during long contraction times. Then we have to consider factors, like length-tension curve, isokinetic vs isotonic/isoinertial contractions, the type of motor unit activation (‘synchronous versus asynchronous’ versus Henneman’s size principle). Add to this differences in not only tension but other factors that will impact on the client, like force output and even hormonal and metabolic factors [For example: LOW INTENSITY [lighter loads] exercise with slow movement has been found to acutely increased anabolic hormone concentrations - regardless of time to complete the CON and ECC actions (5-1 vs 1-5 vs 3-3 vs 1-1) - From Goto, K., Ishii, N. Kizuka, T. et al., (2009) ‘Hormonal and metabolic responses to slow movement resistance exercise with different durations of concentric and eccentric actions’, European Journal of Applied Physiology, 106 (5), pp. 731-739.

So my decision to manipulate load versus speed comes from the training intent (client’s goals, needs and training/injury history) and I often manipulate both in a periodised fashion. Eg. manipulate load, then as the training gains plateau, manipulate movement speed or visa-versa. I have tried to keep it short (we could go for another two articles) but address all points. Hope this covers everything. For further clarification on a given area please just add a post and I will respond. Fun In Training. Rob

Wahid, Nabil | 23 Oct 2010, 23:52 PM

according to Carolyn Kisner and Lynn Allen "Therapeutic Exercise 5th edition page # 171"
" a common error made by some weightlifters during high-intensity resistance training is tl assume that if a weight is lifted quickly (concentric contraction) and lowered slowly (eccentric contraction), the slow eccentric contraction generates greater tension. in fact, if the load is constant, less tension is generated during the eccentric phase. the only way to develop greater tension is to increase the weight of the applied load during the eccentric phase of each exercise cycle. this usually requires assistance from an exercise partner to help lift the load during each concentric contraction. this is a highly intense form of exercise and should be undertaken only healthy infividuals training for high-deand sports or weightlifting competition. this technique is not appropriate for individuals recovering from musculoskeletal injuries.

my question to Rob Orr, do you think both factors (time and load) have the same influance on tension generation? thanks

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